Hi:
My name is Tom. I have 97 Volvo 850 Turbo LE. Just bought from relative 2 months ago. 76k miles.

Has anyone else had this problem. We had one of the O2 sensors replaced and new plugs and oil change. ($500) After a week the oil was black again and the smoke was still sometimes black. Still had soot coming from tail pipe. Runs okay but using a lot of gas. Check engine light on. My mechanic is pretty good but he is puzzled and hesitant. Checked with previous owner and they had problem for a while but said it was cured by cleaning O2 sensors. Any thoughts out there?

Tom K

I had a similar but more pronounced problem on my 854 t. It was the piping from the turbo to the intake, basically was loose, then fell off. This caused an over rich condition due to lack of boost. Does the boost feel weak? A loose clamp on the hose can create enough of a leak to cause the problem, the engine is always using some boost, so without the correct amount, it runs too rich.
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Wills 98 R AWD modded wagon 94 854 T some mods 92 740 wagon

Tom - Did you get any maintenance records from the previous owner?

If not, I would take the car to a dealer and have them do a good check of the car. My dealer will do a check as if they were going to certify the car an give me a two page written report, including a compression test, for three hours labor.

Go over the results of the check with a good advisor or tech and formulate a strategy to correct any problems. Fix what you can, yourself.

Often, a major service can remedy many problems in a cost effective manner. Fluid changes are a good idea also.
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3 8s & 2 7s 725,000 miles total

Tom:
next to the engine temperature and O2 sensors, the likely culprit is is the fuel pressure regulator which is located on one end of the fuel rail. in any case get the error code by interrogating the check engine light system and fix the problem quickly as the rich fuel condition can damage your catalytic converter (happened to me on my previous volvo, a 740gle). also, you will need a new set of spark plugs after the problem is fixed.

yt
855, 5spd, non-turbo

What is your temp gauge telling you? Should run around 3:00 position. I'm thinking coolant temp sensor could be faulty, signalling cold temps and calling for richer mixture?

I'd guess the air filter was replaced when you had the tune-up performed.
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Erwin in Memphis, '95 855t

The CE light comes on for a failure in the emissions system and can be caused by a number of reasons (airpump, fuel delivery system, EGR, O2 sensors, etc.). Have you had the car scanned for codes? By a qualified Volvo specialist?

The mileage is pretty low for a turbo failure, but you want to have this checked out....by someone who knows what they're talking about. (I don't think this is the problem as these turbos usually run to ± 250K miles, but you should put this theory to rest so you can sleep at night.)

One of the first signs of impending turbo failure is oily blue smoke from the tailpipe on high-boost starts, such as from stop signs and red lights, which then seems to clear up a few seconds later. This is caused by a failure of the rear shaft oil seal, which allows pressurized oil to mist into the exhaust manifold. (Oil in the intercooler duct, and carbonized oil on the turbo's exhaust-side impeller are absolutely normal - don't let them tell you need a turbo because they see oil here.)

Another possibility would be the crankcase ventilation system, which may be clogged and thus forcing hot oily crankcase gases to blow by the rings and into your exhaust. In fact, this is more likely.

A failed 02 sensor wouldn't have much to do with whether oil is getting to the exhaust.
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David \\ (98 S70 T5SE Black, misc mods (mostly lighting), red calipers) (92 940GLE)

flush the engine with a good engine flush. car must have mostly city miles and so the accumulation of a lot of stuff. also....what do you mea by "a lot of oil" and "a lot of gas"??? please give concrete numbers. a "lot" to you may be normal for the car.